The chemical composition of biominerals is essential for understanding biomineral formation and is regarded as an attractive subject in bio-mineralogical research on human kidney stones (urinary calculi). In order to obtain more geochemically interpreted data on biogenic minerals, mineralogical compositions and major and trace element concentrations of sixty-six kidney stone samples derived from kidney stone removal surgeries were measured. Infrared spectroscopy results showed that calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) were the two main mineral components of kidney stones. Geochemical results indicated that major and trace element concentrations were present in the following order: Ca > Mg > Na > K > Zn > Fe > Pb > Ba > Cu > Ti > Mo > Cd > Cr. With the exception of Ca, Mg was the second-most abundant element. Zn exhibited higher concentrations relative to other trace elements, which suggests a potential substitution of calcium by metal ions with a similar charge and radius rather than by metals in kidney stone formation. Pb appeared in significantly higher concentrations than in previous studies, which indicates Pb enrichment in the environment. In order to discern multi-element relationships within kidney stones, principal component analysis was applied. Three principal components (PCs, eigenvalues >1) were extracted to explain 64.4% of the total variance. The first component exhibited positively correlated Na-Zn-Cr-Mo-Cd-Pb, while the second component exhibited more positively weighted Mg-K-Ba-Ti. Fe-Cu demonstrated a positive correlation in the third component. This study suggests that Ca exhibits a preference for uptake by oxalates during human urinary stone crystallization, while other alkali metals and alkaline earth metals precipitate with phosphate.

Human agricultural activities have resulted in widespread land degradation and soil contamination in the karst areas. However, the effects of reforestation after agricultural abandonment on the mobility risks and contamination of heavy metals have been rarely reported. In the present study, six soil profiles were selected from cropland and abandoned cropland with reforestation in the Puding karst regions of Southwest China. The Community Bureau of Reference (BCR) sequential extraction method was used to evaluate the compositions of different chemical fractions of soil heavy metals, including Fe, Mn, Cr, Zn, Ni, and Cd. The total contents of Cr, Ni, Zn, Cd, and Mn in the croplands were significantly higher than those in the abandoned croplands. For all soils, Cr, Ni, Zn, and Fe were mainly concentrated in the residual fractions (>85%), whereas Mn and Cd were mostly observed in the non-residual fractions (>65%). The non-residual fractions of Cd, Cr, Ni, and Zn in the croplands were higher than those in the abandoned croplands. These results indicated that the content and mobility of soil heavy metals decreased after reforestation. The individual contamination factor (ICF) and risk assessment code (RAC) showed that Cd contributed to considerable contamination of karst soils. The global contamination factor (GCF) and potential ecological risk index (RI) suggested low contamination and ecological risk of the investigated heavy metals in the croplands, moreover they can be further reduced after reforestation.

As emerging contaminants, rare earth elements (REEs) have undergone significant anthropogenic enrichment in aquatic systems. This study investigates the REE concentrations, major metal elements, and grain size in surface sediments from the East Tiaoxi (ETX) River in eastern China, a small urban river subjected to substantial anthropogenic influences. Total REE concentrations of surface sediments ranged from 133.62 to 222.92 mg/kg with MREE enrichment and HREE depletion. REE concentration and fractionation were strongly correlated with Ca, Fe, Mg, and Mn, which may reflect the control of clay minerals, Fe-Mn oxides, and specific heavy minerals, and differences in REE behavior between riparian sediments and riverbed sediments highlighted the impact of hydrodynamic sorting and chemical weathering on REE distribution. Anthropogenic activities, particularly urbanization, were found to increase REE concentrations, especially at urban-adjacent sites (e.g., RBS2 and RS2), while natural processes such as soil transport and chemical weathering primarily contributed to REE variation at other sites. The enrichment factor and ecological risk assessment revealed that the enrichment and moderate risks associated with REEs occurred in river sediments adjacent to urbanized areas, though agricultural impacts were less pronounced. The findings emphasize the combined influence of urbanization and natural processes on REE distribution and ecological risks in the ETX River basin and underscore the need to prioritize urban-derived REE contamination in environmental management strategies.

In coastal rivers with various human and damming activities (reservoir), the cycle and biogeochemistry of environmental pollutants in river systems has been modified. A total of 42 suspended particulate matter (SPM) samples were obtained in Jiulongjiang River, southeast China to investigate the concentration, sources, behavior, and risks of nine potentially toxic elements (PTEs) in SPM. The results of metals concentration showed relatively large variation, major for Mn and minor for Co; Mn > Zn > V > Pb > Cr > Ni > Cu > Cd > Co. Multi-index evaluation reflected that most of the PTEs are minor enrichment/moderately polluted. The Cd is defined as extremely severe enrichment/polluted level, and the Pb and Zn as minor enrichment/moderately polluted levels. Among the selected PTEs, Cd and Zn are identified as the main toxic factors of SPM with a contribution of 57 ± 18% and 14 ± 7% to the total toxic risk. The sources identification suggested that human inputs may be the primary potential source of Cd, Zn, Pb, and Co, whereas natural sources (e.g., rock weathering) are likely to be responsible for Cu, Cr, V, and Ni. In contrast, the data suggested that Mn may be attributed to both natural and anthropogenic inputs. The PTEs among dissolved, suspended, and sediment phases reflected the transportation behavior and different potential risk levels. Overall, the PTE geochemistry of river SPM can act as a good indicator of the driving mechanism of PTEs’ accumulation and provide a powerful support for controlling riverine PTEs-related pollution in coastal regions.